In fact, someone put a Dow 20,000 hat on his desk, and it was downright radioactive in his mind. The last thing he wanted to see was a video of himself wearing the hat if the market ended up rolling over.

No one knows which way he market go. The downside is way too big, and the upside is nil, he said. Investors have been burned too many times. That is why he takes a clinical way to assess the stocks that led the charge to 20K, like Visa, Home Depot and Apple.

"You have to do it clinically because at any given time, if the stocks get truly overheated, you need to be willing to cut and run. Even then it is dangerous," the "Mad Money" host said.

Michael Nagle | Bloomberg | Getty Images

A "Dow 20,0000" hat sits on a desk at the New York Stock Exchange on Wednesday, Jan. 25, 2017.

The key, Cramer said, is to look for anomalies. Those are stocks that aren't too late to buy and aren't as much as they should be versus their fundamentals. He also warned to stay away from groups that could hurt investors, like retail and drugs.

Retail is key, because of the Amazon factor and a potential border tax that President Donald Trump has said he intends to impose. Trump could also aim a vicious tweet at healthcare and drug companies.

There is no celebration for Cramer. Instead, he rolls up his sleeves to find the stocks of high-quality companies, and then does his homework. Anything that is wishy-washy just won't cut it for him.

"Don't cheer-lead, but don't sow fear and don't dismiss: it is just as important to keep people out as it is to put people in, except the first one has been wrong and the second has been right," Cramer said.